1. Field of the Invention
The present invention relates to a touch device and method, and more particularly, to a capacitive sensing device and method.
2. Description of the Prior Art
Referring to FIG. 1, a diagram depicting a prior-art capacitive sensing device with multi-touch operations and a capacitance image is shown. A touch panel 110 has a plurality of first conductive lines 112 and a plurality of second conductive lines 114. The first and second conductive lines are perpendicularly stacked on and electrically isolated from each other. When a sensing signal (not shown) is input to one of the first conductive lines 112, it creates a plurality of capacitive coupling with all of the second conductive lines at intersecting points, thereby determining the electrical characteristics of the intersecting points based on the current or voltage on all of the second conductive lines. Each of the first conductive lines 112 are sequentially provided with the sensing signal, and the electrical characteristics of all the intersecting points can be determined by the sensing process just described.
When a human, naturally grounded, touches or gets near a sensing location (an intersecting point) with his/her finger tip, the coupling capacitance of the sensing location is influenced, that is, current or voltage thereof is changed. However, when there are two touch points P1 and P2 on the touch panel 110, not only the current or voltage at touch points P1 and P2 would change, but also the current or voltage at two other intersecting points G1 and G2 (forming the so-called “Ghost points”). Thus, two touch points P1 and P2 will result in the current or voltage change in four intersecting points on the touch panel 110 (e.g. (X1, Y4), (X3, Y6), (X1, Y6) and (X3, Y4)) and the actual touch points cannot be identified. Explain further from the capacitance image 120, the capacitance image wave P1W1 of a touch point P1(X1, Y4) is different from the capacitance image waves G1W1 and G2W1 of intersecting points G1(X1, Y6) and G2(X3, Y4) by d1 and d3, respectively; the capacitance image wave P2W2 of a touch point P2(X3, Y6) is different from the capacitance image waves G1W1 and G2W1 of the intersecting points G1(X1, Y6) and G2(X3, Y4) by d4 and d2, respectively. However, the magnitudes of d1˜d4 are too small to make use, and sensing can be easily affected by noises, thus multi-touch operations are often mistakenly determined.
In view of these problems, the present invention provides a capacitive sensing method and device, which improves the problem with multi-touch operations and effectively makes use of a current or voltage difference generated as a result of touching.